This invention relates to recessed encapsulated microelectronic devices, and methods for forming such encapsulated devices.
Packaged microelectronic assemblies, such as memory chips and microprocessor chips, typically include a microelectronic device mounted to a substrate and encased in a plastic protective covering. The device includes functional features, such as memory cells, processor circuits and interconnecting circuitry. The device also typically includes bond pads electrically coupled to the functional features. The bond pads are coupled to pins or other types of terminals that extend outside the protective covering for connecting the microelectronic device to buses, circuits and/or other microelectronic assemblies.
In one conventional arrangement, shown in FIG. 1, a packaged device 50 includes a substrate 10 (such as a printed circuit board or xe2x80x9cPCBxe2x80x9d) having an upper surface 11 and a lower surface 12. The substrate 10 includes conductive substrate pads 14 on the upper surface 11 connected to ball pads 15 on the lower surface 12 by a plurality of vias 16. A microelectronic die 30 having die bond pads 31 is positioned on the upper surface 11, and the die bond pads 31 are connected with to the substrate pads 14 by wire bonds 32. The microelectronic die 30 is then encapsulated with an encapsulating material 40 to protect the die 30 and the wire bonds 32. Solder balls can then be connected to the ball pads 15 for linking the die 30 to a circuit or another device.
In another conventional arrangement, shown in FIG. 2, a package 50a can include a lead frame 25 having lead fingers 27 positioned adjacent to the die 30. In one aspect of this arrangement, the lead frame 25 can include a paddle (not shown) that extends between the lead fingers 27 to support the die 30. Alternatively, the paddle can be replaced with a layer of thermoset adhesive material 17 that extends between the lead fingers 27 and supports the die 30. The thermoset material 17 is then heated to bond the material to the die 30, and the bond pads 31 on the die 30 are wire bonded to the lead fingers 27. An encapsulating material 40a is disposed over both the die 30 and the thermoset material 17 to form the package 50a, and the ends of the lead fingers 27 are bent to form pins 26 for connecting the die 30 to other devices or circuits.
The packages 50 and 50a described above with reference to FIGS. 1 and 2 can suffer from several drawbacks. For example, the overall height H of the packages 50 and 50a may be so large that it is difficult to integrate the packages with low-profile electronic products, such as mobile telephones and hand-held or laptop computers. Furthermore, it may be difficult to transfer heat from the dies 30 because the dies 30 are surrounded on all sides by materials having low thermal conductivities. For example, the die 30 shown in FIG. 1 is surrounded by the encapsulating material 40 and the substrate 10, and the die 30 shown in FIG. 2 is surrounded by the encapsulating material 40a and the thermoset material 17. It is particularly important to dissipate heat in high-speed microprocessors and memory devices to maintain the performance levels of these devices. Thus, the package 50 and 50a may not be adequate for use in many types of products.
The present invention is directed toward microelectronic device packages and methods for forming such packages. A method in accordance with one aspect of the invention includes positioning a microelectronic device at least partially within a cavity of a support member having a first surface and a second surface facing opposite the first surface, with the cavity extending through the support member from the first surface to the second surface. The method can further include supporting the microelectronic device relative to the cavity with a removable retention member. The microelectronic device is electrically coupled to the support member and a portion of the microelectronic device is encased with an encapsulating material. The removable retention member is then removed from the support member.
In a further aspect of the invention, the microelectronic device has a first face and a second face facing opposite the first face. The second face of the microelectronic device is initially engaged with the removable retention member and is exposed when the removable retention member is removed. In still a further aspect of the invention, a heat transfer material can be applied to the second face of the microelectronic device to conduct heat away from the microelectronic device.
The invention is also directed toward a microelectronic device package. In one aspect of the invention, the package can include a support member having a first surface, a second surface facing opposite the first surface, and a cavity extending through the support member from the first surface to the second surface. The support member defines a first region extending outwardly from the first surface and a second region extending outwardly from the second surface. A microelectronic device having a first face and a second face facing opposite the first face is disposed in the cavity. The package further includes an encapsulating material positioned in the first region defined by the support member, but not in the second region, such that the encapsulating material at least partially surrounds the microelectronic device adjacent to the first face of the microelectronic device.